1. Field of the Invention
The present method is directed to systems and methods for using ionized metal cluster beams and, more particularly, to depositing metal bumps on electrical substrates and removing undesired deposits around the bumps, to depositing alloyed bumps with constant compositions, and to cleaning metal out of focusing apertures.
2. Description of the Related Art
Recently, most of the high performance electronic systems demand that either tape-automated-bonding (TAB) or flip chip bonding be used as compared to wire bonding to attach integrated circuit chip leads to high density interconnect boards. These types of bonding require that the chip interconnect pads be higher than the rest of the chip. Preferably, such pads are metal bumps anywhere between 1 and 20 microns thicker than 1 micron thick aluminum typically required for wire bonding.
However, chips normally have only thin metal pads for wire bonding and are not available with thick bumps. Thick bumps can be manufactured by the time-consuming process of photolithography using either a bump plating process or lift-off process.
Needless to say, there is a need for systems and methods designed to rapidly and reliably manufacture thick metallic bumps (such as of gold and tin-lead alloys) on chips and other substrates in microelectronic applications.